Interionic energy transfer in Y3Al5O12:Ce3+, Pr3+ phosphor

We present an investigation of dynamical processes of nonradiative energy transfer (ET) between Ce3+ and Pr3+, and between Pr3+ ions in Y3Al5O12:Ce3+, Pr3+ phosphor. Photoluminescence spectroscopy and fluorescence decay patterns are studied as a function of Pr3+ and Ce3+ concentrations. The analysis based on Inokuti–Hirayama model indicates that the ET from the lowest 5d state of Ce3+ to the D12 state of Pr3+, and the quenching of the D12 state through a cross relaxation involving Pr3+ ions in the ground state are both governed by electric dipole–dipole interaction. An increase in the Ce3+–Pr3+ ET rate followed by the enhanced red emission line of Pr3+ relative to the yellow emission band of Ce3+ on only increasing Ce3+ concentration is observed. This behavior is attributed to the increase in the spectral overlap integrals between Ce3+ emission and Pr3+ excitation due to the fact that the yellow band shifts to the red spectral side with increasing Ce3+ concentration while the red line dose not move. For Ce3+ concentration of 0.01 in YAG:Ce3+, Pr3+, the rate constant and critical distance are evaluated to be 4.5×10−36 cm6 s−1, 0.81 nm for Ce3+–Pr3+ ET and 2.4×10−38 cm6 s−1, 1.30 nm for Pr3+–Pr3+ ET. Spectroscopic study also demonstrates a pronounced ET from the lowest 4f5d of Pr3+ to the 5d of Ce3+. A proportional dependence of the initial transfer rate on acceptor concentration is observed in each of these ET pathways. The proportional coefficient as the averaged ET parameters for initial decay are determined, meaning the ET efficiency for the same concentration of acceptors follows the order of Pr3+–Pr3+>Pr3+–Ce3+>Ce3+–Pr3+.